Frame time base for television receivers

ABSTRACT

A frame time base system for television receivers and the like. The system is built around a cold-cathode glow discharge tube having an anode, a grid, a trigger electrode and a cathode, a first source of positive potential connected to the anode through a first resistor, a capacitive network connected to the anode and the first resistor to form a sawtooth wave generator for the output of the discharge tube, a resistor network connected between the trigger electrode and the grid, a source of synchronizing pulses supplied through the first portion of the resistor network to the triggering electrode and through a second portion of the resistor network to the grid, and a second source of positive potential connected through a second resistor to the resistor network.

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[111 mums [72] Inventors Leonid Mikhailovich Tikholmirov U.S.S.R. [211App]. No. 749,391 [22] Filed Aug. 1, 1968 [45] Patented Dec. 14, 1971[S4] FRAME TIME BASE FOR TELEVISIIO RECEIVERS 5 Claims, 1 Drawing Fig.

[52] US. 1 323/181, 315/241, 315/245, 328/67, 328/84, 328/210. 328/250,331/131 [51] Int. Cl H03lt4/12 [50) Field of Search. 328/67, 210,21 1,181, 84,250; 331/131; 315/24l,245

[56] References Cited UNITED STATES PATENTS 2,058,738 10/1936 St.Laurent 328/210 2,185,189 1/1940 Germeshausen 315/241 X 2,578,52512/1951 Erickson 328/67 X 2,591,511 4/1952 Clarke 328/210 X 2,883,5354/1959 Creveling et a1. 328/210 3,113,240 12/1963 Perkins etal. 328/67 XPrimary Examiner-John S, Heyman Assistant Examiner-R. C. WoodbridgeAttorney-Waters, Roditi & Schwartz ABSTRACT: A frame time base systemfor television receivers and the like. The system is built around a coldcathode glow discharge tube having an anode, a grid, a trigger electrodeand a cathode, a first source of positive potential connected to theanode through a first resistor, a capacitive network connected to theanode and the first resistor to form a sawtooth wave generator for theoutput of the discharge tube, a resistor network connected between thetrigger electrode and the grid, at source of synchronizing pulsessupplied through the first portion of the resistor network to thetriggering electrode and through a second portion of the resistornetwork to the grid, and a second source of positive potential connectedthrough a second resistor to the resistor network.

FRAME TIME EASE EUR TELEVWIION RECEIVERS The present invention relatesto television, and more particularly to frame time base systems fortelevision receivers. The prior art includes frame time bases fortelevision receivers, using cold-cathode glow discharge tubes. in suchtime bases, the tube has a cathode, a trigger electrode, a grid, and ananode sequentially arranged. The trigger electrode serves to reduce theerratic delay in starting the main-gap discharge and is connected to asource through a currentlimiting resistor. The grid is held positivewith respect to the cathode and is fed frame-synchronizing pulses.

A disadvantage of prior art frame time base systems is that variationsin the starter-gap discharge current, bias voltage or supply voltageimpairs the synchronization such that additional controls are providedfor adjustment.

Another disadvantage is that such time base systems require high-qualityresistors, capacitors and tubes manufactured to extremely closetolerances.

An object of the present invention is to provide a frame time basesystem which dispenses with the need for additional adjustment controlsand is capable of stable synchronization even under the influence ofmarked variations in the voltages applied and the ratings of the circuitcomponents. I

This and other objects are accomplished in accordance with theprinciples of the present invention by providing a frame time basesystem using a cold-cathode glow discharge tube whose anode circuitcontains an RC-network to produce a sawtooth voltage, in which,according to the invention, there are resistors placed between thetrigger electrode and the grid in order to decrease the grid potentialwith respect to the trigger electrode in the course of time baseoperation, while the circuit through which the grid is fed synchronizing(sync). pulses contains some of these resistors whose resistance is madesufficiently high to prevent relaxation oscillations occurring in theelectrode circuits.

Connection of the tube electrodes and the injection of sync. pulses,according to the invention, the anode breakdown voltage is held fixedand the stability of synchronization is maintained due to the fact thatvariations in the starter gap discharge current compensate forvariations in the grid potential.

The invention will be more fully understood from the followingdescription of a preferred embodiment, when read in connection with theaccompanying drawing which is a schematic diagram of a frame time basesystem for television receivers, according to the invention.

A frame time base system, according to the invention, comprises acold-cathode glow discharge tube 1 in which a trigger electrode 2 and agrid 3 are sequentially arranged between a cold cathode l and an anode5. Connected to the anode 5 is an RC-network network made of a resistor6 connected to a source E and series capacitors 7 and ii. The capacitorh blocks the DC component due to E, from the sawtooth voltage derivedacross the capacitor 7. The trigger electrode is connected through aresistor 9 to another source E in some cases, the resistors 6 and 9 maybe connected to the positive side of a common source. The grid 3 isconnected through series resistors 10 and ill to the trigger electrode2. The vertical scan sync. pulse source (omitted in the schematic) isconnected to the common junction of the resistors 10 and 1111 through aDC blocking capacitor 112.

The connection of the vertical scan sync. pulse source through thecapacitor 112 as shown in the schematic may cause relaxationoscillations in the trigger electrode and grid circuits; to preventthem. the resistors 110 and ill have sufficiently high values ofresistance.

The output sawtooth voltage of the frame time base herein disclosed isderived in the conventional manner. The capacitors 7 and 8 are chargedby the source E, through the resistor 65. When the anode voltage reachesthe breakdown value or when a sync. pulse is applied to the grid 3through the resistor lit the capacitors 7 and h discharge through thetube l. The relatively low rate of charge of the capacitor 7 and itsrapid dischar e result in sharp sawtooth voltage pulses at the output.The etailed description that follows describes the portion of the timebase responsible for the stable synchronization of the frame frequency.

When the supply voltage is turned on, a triggering discharge occursacross the startergap between the trigger electrode 2 and the cathode 3,characterized by a constant voltage drop over a broad range of current.Since the grid 3 is placed near the trigger electrode 2, a transfercurrent begins to flow between the grid and the starter-gap discharge,giving rise to a voltage drop across the resistors and ill and reducingthe potential at the grid 3 relative to the trigger electrode 2. Thetransfer current and, consequently, the fall of the grid potentialincrease with increase of the starter-gap current. In coldcathode glowdischarge tubes, the anode breakdown voltage decreases with increase ofstarter-gap current and of grid potential.

Thus, connection of the electrodes 3 and 2 through the resistors lit)and ill provides for the stabilization of the anode breakdown voltage.if, for example, the starter-gap current should increase due to anincrease in the supply voltage or the aging of the resistor 9 or thetube 1, the transfer current will also increase, further decreasing thepotential at the grid 3, thereby stabilizing the anode breakdownvoltage. A decrease in the starter-gap current reduces the potential atthe grid 3, and the anode breakdown voltage is again stabilized.

From the foregoing it follows that the anode breakdown voltage remainspractically constant against variations in supply voltage, tubecharacteristics, or resistor ratings. As a result, the synchronizationof the frame frequency is stabilized to a high degree.

The invention herein disclosed provides for stable synchronization withsmall-amplitude sync. pulses against marked variations in supply voltageand two-fold changes in resistor ratings, and also makes redundant anysynchronization adjustment controls.

What is claimed is:

l. A frame time base system for television receivers and the likecomprising a cold-cathode glow discharge tube having an anode, a grid, atrigger electrode and a cathode, a first source of positive potentialconnected to said anode through a first resistor, a capacitive networkconnected to said anode and said first resistor to form a sawtooth wavegenerator for the output of said discharge tube, a resistor networkconnected between said trigger electrode and said grid, a source ofsynchronizing pulses supplied through a first portion of said resistornetwork to said triggering electrode and through a second portion ofsaid resistor network to said grid, and a second source of positivepotential connected through a second resistor to said resistor network.

2. A system as claimed in claim 1, wherein said capacitive networkinclude, first and second capacitors connected in series between saidanode and a point of ground potential, said sawtooth waveform beingdeveloped across said second capacitor.

3. A system as claimedin claim ll, wherein said resistor network isformed by third and fourth resistors connected in series, saidtriggering electrode connected to one end of said third resistor, saidgrid connected to one end of said fourth resistor, said source ofsynchronizing pulses applied to the other ends of said third and fourthresistors, said other ends being connected together.

it. A system as claimed in claim 3, including a third capacitor whereinsaid source of synchronizing pulses are supplied to said other ends ofsaid third and fourth resistors through said third capacitor, said thirdand fourth resistors being of a sufficiently high value to preventrelaxation oscillations.

5. A system as claimed in claim il, wherein said first and secondsources of positive potential are the same.

1. A frame time base system for television receivers and the likecomprising a cold-cathode glow discharge tube having an anode, a grid, atrigger electrode and a cathode, a first source of positive potentialconnected to said anode through a first resistor, a capacitive networkconnected to said anode and said first resistor to form a sawtooth wavegenerator for the output of said discharge tube, a resistor networkconnected between said trigger electrode and said grid, a source ofsynchronizing pulses supplied through a first portion of said resistornetwork to said triggering electrode and through a second portion ofsaid resistor network to said grid, and a second source of positivepotential connected through a second resistor to said resistor network.2. A system as claimed in claim 1, wherein said capacitive networkincludes first and second capacitors connected in series between saidanode and a point of ground potential, said sawtooth waveform beingdeveloped across said second capacitor.
 3. A system as claimed in claim1, wherein said resistor network is formed by third and fourth resistorsconnected in series, said triggering electrode connected to one end ofsaid third resistor, said grid connected to one end of said fourthresistor, said source of synchronizing pulses applied to the other endsof said third and fourth resistors, said other ends being connectedtogether.
 4. A system as claimed in claim 3, including a third capacitorwherein said source of synchronizing pulses are supplied to said otherends of said third and fourth resistors through said third capacitor,said third and fourth resistors being of a sufficiently high value toprevent relaxation oscillations.
 5. A system as claimed in claim 1,wherein said first and second sources of positive potential are thesame.